1. Field of the Invention
The present invention relates to devices for producing metal rings, and more particularly to devices for curling metal plate members to produce rings. More specifically, the present invention is concerned with metal ring producing devices of a so-called "double roller" type which comprises a rigid roller and a resilient roller between which the metal plate member is inserted to be curled for production of the metal ring.
2. Description of the Prior Art
For producing metal rings, the double roller type devices have been hitherto employed. Some of them are shown in "Press Working Handbook" issued Oct. 25, 1975 from MARUZEN CO., LTD. As is shown in FIG. 12 of the accompanying drawings, in these devices, a rigid roller 13 and a resilient roller 11 are used which are arranged in parallel keeping a slight contact therebetween. When, as shown in the drawing, a metal plate member 15 having a given length is inserted between the rigid and resilient rollers 13 and 11 and then the resilient roller 11 is rotated in the direction of the arrow "11a", the metal plate member 15 is curled and finally wound around the rigid roller 13 in a manner as shown in FIG. 13. The curled plate member 15, which is thus shaped like a ring 17, is removed from the rigid roller 13 and then welding is applied to opposed edges of the ring 17 to complete the same.
For ease of description, in the following, the ring which has not been subjected to the welding will be referred to just "ring", while, the ring which has been subjected to the welding will be referred to "finished ring".
As shown in FIG. 14, the resilient roller 11 comprises two opposed circular flanges 19, a cylindrical core portion 21 concentrically disposed between the two flanges 19 and an elastic annular member 23 put around the core portion 21. The elastic annular member 23 is bonded to the core portion 21. As shown, peripheries of the flanges 19 extend radially outward beyond an outer surface of the elastic annular member 23 thereby to define therebetween a shallow annular groove 19a. The elastic annular member 23 is a rubber ring, a soft plastic ring or the like. The shallow annular groove 19a is shaped and sized to neatly receive the metal plate member 15 (or the ring 17 put around the rigid roller 13).
In order to remove or release the ring 17 from the rigid roller 13, the conventional double roller type device has a roller shifting mechanism (not shown) by which one of the two rollers 13 and 11 is moved away from the other to define a certain clearance between the two rollers 13 and 11. However, usage of such roller shifting mechanism makes the device complicated in construction, and operation of such roller shifting mechanism causes the device to fail to exhibit a satisfied production speed of the rings 17.